Pile-driving apparatus



April 15, 1958 H. P. BURRELL 2,830,443

PILE-DRIVING APPARATUS Filed Jan. 11, 1955 4 Sheets-Sheet 1 m w 4 WP 360i? 4 i fw w ,w u n y IIL y 5W 4 u 5 4 4 z f M n ma W ,d m

April 15, 1958 H. P. BURRELL 2,830443 PILE-DRIVING APPARATUS Filed Jan. 11, 1955 4 Sheets-Sheet 2 4 Sfxeets-Sheet 3 April 15, 1958 Filed Jan.` 11, 1955 NCQ April l5, 1958 H. P. BURRl-:LL 2,830,443

PILE-DRIVING APPARATUS Filed Jan. 11, 1955 4 Sheets-Sheet 4 @Il 4 n Z2 Y@ y: 41a

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PILE-DRIVING APPARATUS Harold P. Burrell, Noroton, Conn.

Application January 11, 1955, Serial No. 481,083

3 Claims. (Qi. 61-79) The present invention relates to apparatus for driving the casting shells of armored cast-in-place concrete piles and a method of forming the latter.

A general object of the present invention is to provide unique mandrel equipment which may be easily and efficiently expanded within a lcasting and armoring shell to clamp the latter thereto for effective driving with light travelling equipment while maintaining ground pressure on the shell, with provision of an interior feeder passage for ready delivery to the bottom of the mandrel means of charges of unset footing concrete, the mandrel equipment also including tamping means for compacting such concrete charges into a base or footingmass at the bottom of the shell prior to mandrel removal, and a novel method of driving and forming shell-armored cast-in-place concrete pile having a desired tamped base or footing of concrete of excellent `load-bearing characteristics. The terml concrete as used herein is intended to cover any suitable footing material, such as stone, gravel or slag, whether used plain or mixed with binder.

A more specific object of the invention is to provide such mandrel equipment which is characterized by a hollow rigid mandrel tube sheathed with inilatable chamber means for secure clamping and support thereon of the usual type of corrugated steelfshell to be driven veffectively into the ground with the mandrel tube, the

latter having loosely telescoped thereinto a core tube providing a footing concrete feeder conduit and having a tamping bottom end for compacting and shaping masses of footing concrete delivered therethrough into a loadbearing base for the pile prior to removal of the mandrel and core tubes and subsequent filling of the shell with concrete.

Another object of the present invention is to provide` hollow driving mandrel means in the form of a rigid driving tube having an elongated imperforate section surrounded by a shell-supporting sheath of elastic material defining therebetween an expandable and collap- `sible chamber with the tube being provided exteriorly,

Ain at least one locality and preferably a plurality thereon; with circumferentially-spaced.lands so that when one or more cinching bands snug the sheath at such localities to the tube thereat for anchorage to the tube to resist during driving undue distortable and damaging longitudinal .drag fluid passages are maintained along the lands whereby all cinch band-defined sections of the sheath are properly inflatable and deliatable.

A further.A object of `the invention is to provide for such a hollow driving mandrel a hollow core tube which may be loosely and withdrawably telescoped thereinto to provide a through feeder conduit through which charges of unset concrete may be fed to the vicinity of the bottom of acasting and Varmoring shell driven by the mandrel, the bottom end ofthe core tube being so shaped and/or constructed as to provide a passaged concrete tamping means for effectively compacting unset footing concrete after being delivered therethrough, and prior to any required removalV of mandrel means for subsequent cast- 'ing of the pile core. Y

Prior to the present invention two general methods `have been employed in forming shelled cast-in-place con- 5 crete piles which may be identified as V(l) the blocked mandrel method and (2) the casing pipe procedure. In Athe blocked mandrel method the shell is clampedV upon an expanded driving mandrel which has a blockedinterior preventing feed of material therethrough, and theqshell Y is driven by the mandrel with maintenance of pressure between the shell and ground. Such driving of the shell may be accomplished by light and 'readily portable equipment such as a crawler crane, but once the shell has been driven into place its form cannot be altered as by adding a useful enlarged base. ln the casing pipe procedure a heavy driving pipe having a closing boot pan is driven into the ground by heavy equipment; the shell is then dropped into it and the casing pipe is drawn up from about the shell. The casing pipe does provide a feeder conduit for delivery of footing concrete priorV to the setting of the shell thereinto but when the casing pipe is withdrawn from about the shell there may be such soil suction and disturbance as to reduce or destroy the potential load-bearing quality of the pile to be cast in lthey shell and'in any event the soil-to-shell pressure is undesirably low. in line water-bearing sand and other loose soil material suction produced by withdrawal of the casing pipe may withdraw the soil `material from below the pile point or formed footing. These and other difficulties Aof the prior art procedures are efficiently minimized and avoided by the present invention.

A still further object of the present invention is to provide structural embodiments of the apparatus and parts thereof which are readily constructed and assembled and permit eflicient use and operation thereof in the practice of varied procedures best suited to dierent conditions;

, Otherobjects of the invention will in Lpart be obvious and will in part appear hereinafter. 40 The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of theothers, and the apparatus embodying features of construction, 'combinations of Velements and arrangement of parts which are adapted to effect such steps, all as exemplified in the following detailed disclosure, and the scope of the invention will be indicated-in the claims. yFor a fuller understanding of the nature and objects of the invention reference should be had to the following detailed description taken in connection with the accom- ,panying drawings, in which: v

Fig. l is a side elevational view, with parts broken Hawayanrl in section, of an embodiment of the pile driving apparatus of the present invention, showing a casting and armoring ys hell clamped thereon and with the assem- 'blyresti'ng'upon the ground prior to driving;

Fig. 2 isa side elevational view of the structure shown in Eig. 1 to a smaller scale, showing the assembly in driven position in the ground;

the drivenassembly depicted in Fig. 2, illustrating manipulation of anvil and core tufbe structure thereof permitting dumping into rthe latterof charges of unset footing concrete and delivery thereof to the vicinity of the bottom of the Shell;

Fig. 4 is an enlarged cross-sectional view of the assembly shown irl-Figs. l, 2 and 3 taken through one of the sheath-snugging cinch bands and illustrating maintenance thereat of longitudinally-extending sheath lluid passages or flow ducts by one form of land means;

Fig. 5 is a cross-sectional view similar to Fig. 4, with `Fig. 3 i s an axial sectiorgwith parts broken away, of

3 parts broken away and omitted, of another form of land which may be used to maintain sheath fluid passages or flow ducts at a cinch band; v

Fig. 6 is an enlarged axial section .of the bottom portion of Fig. 3, illustrating the formation of atampedV bulbousbase or footing of concrete for the pile shell with drive of the latter thereinto;

Fig. 7 is an axial section of the bottom portion of Fig. 1, showing the incorporation the-rein of slip tube means to reduce drag on the mandrel tube during tamping;

Fig. 8 is a perspective view of a blank from which the Fig. 7 slip tube means may be formed;

Fig. 9 is a perspective view of the Fig. 7 slip tube means as formed by shaping the Fig. 8 blank into tubular form;

Fig. 10 is a pictorial section, with parts in elevation, illustrating the manner in which the unfinished slip tube means of Fig. 9 may be completed for use as illustrated in Fig. 7;

Fig. 11 is an enlargedaxial section similar to Fig. 6 illustrating the formation of a` pile base or footing with an assembly in which ythe Figs. 7 to 9 incl. slip tube means is incorporated; and

Fig. 1'2 is an axial section of the bottom portion of a modified form of pile driving apparatus and pile shell assembly illustrating an embodiment of core tube tamping means different from that shown in Figs. 1, 3, 6, 7 and 11 and showing how a precast pile point may be used to advantage with any 4of the depicted forms of driving apparatus. Y

Referring to the drawings, in which like numerals identify similar parts throughout, it will be seen from Figs. l to 4 incl. that an embodiment ofthe present invention may -comprise a mandrel tube or pipe 20, an expandable. and collapsible sheath 21 of elastic material thereon andV a core tube or pipe 22. The mandrel pipe is an elongated, rigid, drivable, unblocked steel tubeor the like which, for example, may berabout 12.75" O. D. and of uniform diameter, having a wall thickness of about 0.5, a weight per foot of about 65.4 lbs. and a length of` about 60. The mandrel tube has an open top end 23 preferably surrounded by a reinforcing Iband 24 welded thereto and serving with the top end edge 0f the tube as abutment means. The bottom end 25 of the mandrel tube 20 is open and the tube interior is unblocked or unobstructed, as shown, for telescopic reception of the core tube 22.

The major portion of the'drive or mandrel tube 20 extending from just below the reinforcing band 24 substantially to the bottom end 2S constitutes an imperforate section of appreciable length intervening the open bottom end and the open top end 23 with the. latter serving as a driving end. This imperforate section carries thereon the expandable and collapsible sheath 21 of suitable elastic material having its upper end secured to the drive tube in a fluid-tight manner -by a head ring 26 to which the sheath maybe clamped by a head band, 27. The bottom end of the sheath 21 is suitably clampedV in a duid-tight manner to the exterior surface of the mandrel tube 20 by a foot band 28. Thus, the sheath 21 and the imperforate section of appreciable lengthof the driving tube 20 covered thereby together define an intervening inflatable and deatable chamber 29. The sheath may have a wall thickness of about 0.5" and maybe formed of reinforced rubber or other suitable elastic material with the reinforcing provided by fabric preferably extending lengthwise to limit longitudinal elongation while permitting free transverse expansion. Fluid under pressure, preferably air, is fed to the chamber 29 by a suitable conduit 30 which, as shown, may be connected through the head ring 26, and this conduit is provided with a valve 31. With the conduit 30 suitable connected to a source of air under pressure manipulationV of the valve 31 will permit the air to flow into the Vchamber 29 and expand Vthe sheathand such valve may be of a two-way type with an outletleading to atmosphere t0` permit deflation of the sheath.

The core tube 22 which is telescop'edV into the mandrel tube 2i) may be about 10.75 O. D. with a wall thickness of about 0.365, having a weight per foot of about 40.5 lbs. and, as shown, extends the full length of the mandrel tube. The upper end 32 of the core tube 22 is open and preferably is provided with a laterally-extending cir-- cumlerential flange 33 to Overlie the upper end 23 of the mandrel tube and its reinforcing ring 24 to serve as the complemental abutment means, limiting downward telescope of the core tube within the mandrel tube. Since the core tube 2.. is to serve as a conduit, its bottom end 34 has a through passage which, in the embodiment of Figs.: l to 4 incl., preferably is valved. Also, the bottom end' 34 of the core tube 22 is to serve as tamping means and thus in the embodiment of Figs. l to 4 incl. it is partially closed by `a cross plate 35, having an outlet passage 36 extending therethrough inthe form of a downwardly facing frustoeconical valve seat. Preferably, a frusto-conical funnelelement 37 is mounted in the core tube 22 above cross plate 35 so as to direct material to .the passage provided by valve seat 36. A head 38 is mated with the valve seat 36 and preferably is carried -on the bottom end of an axially-slidafble rod or stem 39 headed at 40 to provide a limiting stop. The stem 39 is preferably slidably supported in an axiallyarranged section 41 of tubing supported `by suitable spider means 41a, lla from the inner wall of the core tube, as best seen in Fig. i.

The mandrel tube 20 and the core tube 22 telescoped thereinto are surmounted by an anvil 42 preferably in the form of a heavy circular plate having a coaxiallyextending element or skirt 43 yloosely receivable in the upper open end 32 of the core tube. The anvil 42 may be linked by any suitable means, such as clevises 44, 44,

to the base 4S of a steam hammer carried by relatively light portable pile-driving equipment, such as a crawler crane, so that when the hammer is lifted the anvil will be elevated therewith. The anvil 42 preferably carries loops, eyes or other projections 46, 46 which may be connected by suitable sections 47, 47 of flexible tying means, such as lengths of chain or cable, to the top end of the core tube 22, e. g., the lateral flange 33 thereof, by any suitable means, such as ears 4S, 48. Thus, after the anvil 42 is lifted by the hammer base 45 until the flexible ties 47, 47 become taut, further lift of thc anvil with the hammer head raises the core tube 22 while providing a gap between the upper end of the latter and the anvil for supply to the core tube interior of footing material.

As will be more fully explained hereinafter, the mandrel tube 20 is to carry clamped thereto, by the sheath 21 when inflated, the usual type of casting and armoring corrugated shell 49 which is to serve as a form for the cast-in-place concrete pile. Such shell 49 may be a standard 16" cylindrical steel shell having a helical or spiralled shallow and relatively wide groove to form a corrugated tube, as shown in'the drawings, and which may be the product identified by the trade name of Helcor shell. luto the corrugations of this shell 49 the wall of the sheath 21, when inflated, may penetrate about half way or about 0.25" securely to clamp the shell upon the mandrel. For

practical reasons, the maximum length of a cast-in-place armored concrete pile is limited to a length of about 60' and thus the mandrel tube 20 will preferably be provided in a length which may-be no more than a few feet longer than 60.V Since it is intended that the shell 49 be carried into the ground with drive of the mandrel tube 20 against the resistance provided by the drag ofthe shell against the soil, itis a purpose of the present invention to avoid application of undue shear and strain on the sheath 21 and its end anchorages, particularly the one at the bottom provided by the band 28. For this purpose, the sheath 21 is anchored to the mandrel tube 20 at axially-spaced points which may be about 10' apart, more or less, su'cll conical valve' asby cinch bands so-so, eeen-erwin .rods and thus flow ducts will be m 5 chlncfirclesthe sheath and snugs it tothe exterioref thelmandrlf'tube ,to subdivide the spacebetweenthe-mandrel-tube-and inatable sheath, intervening the end anchorageslfo'r -`the intermediate of the Vlongitudina"l-lyexter1dngland rods' 52-52, 'the sheath material will not `be caused tto-dow to contact of all of the side surfaces of'the llongitudinal ainta'ined alojng "the sides of the latter.

In operation and use .of the embodiment Lof,the.figmen-r :tion shown in Figs. 1 to 5 incl. for drivngrandjstting 1armoring shells of cast-.in-place concrete piles, lthe piledriving `apparatus of the present invention. maybesetnp :in the -mannerproposed inl-iig. .1. Letgitsbe' 6 --=thatiah-2alrmoring-sliell .49 V4is-to :serve for f the :castingtnfa tpile :abouts45 long, :and with Vthe soil of'fsuch vlofiseness :thatzthedrag imposed upon the lshellzto be driven byithe :mandrel -requires tying vanchorage ofthe sheath .21 to the latter, into a plurality of 1ongitudinally-succeedingvcom- A5 mandrel :at only three points. `Cinch bands v50.*r'itlavill g partmental sections. Such a cinch f band 50 A-xna-'y 'fbe 'f'.beapplied -to the-lower 45'- length of the sheath :at points formed of webbing and, if desired, `provided "as a str;ap about 155 apart. The'shell 49 iis then :slid over vthetied- 1having suitable fastening or buckle means 151, as -'illustbottom portion .of l'the sheath `21 which, fof course, is yin trated in Fig. 4. v .'deat'ed condition. 'In order to avoid tendencyi'for Ythe Since all sections of the .sheath 2.1 between, succeeding -10 'sheath'lto swelltto the bursting point when inflated above .cinch bands 50, lSi) must be inated to as sure maximum the-topend of the shell 49, .it ispreferably confined by .and ecient clamping anchorage `o f the shell 49 ,UPQD `,the a previously applied top shell section which may bejloosely mandrel, provision mustk be made for vuid connection tied :toY th'e mandrel, such as by vloops 55, 55 of lWire ex-v `between the succeeding sections. In accordance with the tending-through holes 'punched in vthe vtop yedge of .the present invention, such iuid connections ,between sucy'15 Ishell. section =54 and extending throughsuitableears'56,56 ceeding compartmental sections of the indatablesheath preferably mounted on the Vreinforcing band V24'. :The 21 are readily provided by forming,longit11dit1allY-extentl f :anvil 42 will betied tothe hammer. base 145, suclitasxby ing lands on the exterior surface ofthe mandrel tube `clevises 44,44, and thea-nvil then lowered for'telescopic A 2() at least at the locality of each cinch bandSDso Athat recepton of -itsfaxially-extending `tlange 43.into the 4open when the sheath is cinched tightly tovtheiouterpdges pr 2O ytop-end 32 of core 4tube v22. The `ties 47, 47 Iarethcn faces of the lands, free passage is maintained ,along -appliedloosely to connect the anvil to the core tubeV and the Sides of the kinds for ow of air- .As proposed@ the .wholetassembly is rested within a flanged boot'panl57 Figs, 1y 3 and A, such .longitudinallyerrtendirjg.leeds may :resting upon the surface of the soil, as .depicted in Figjl. beprovided as aser-ies Yfc:il'curnfere1111iallyspacxi lopii A Thevalve 31 S then manipulated AS0 `that'. Conduit 30 feeds tudnally-extending rods 52-52 which'may be .offal- L5 :air A'under .pressure from la source of say about l5 p. fs. i..g. eter of about 0.125. Preferably, Such longitndinally- `fto-inilate the sheath v21 and expand rit into clamping extending lands provided by the [Qds 529.52.31@ arranged .Contact Vwith the nllel' Wall fOf the pile Shell 49 andthe substantially over the entire exterior Vsurface .of the improtectiveshell section 54. yThe air under pressure ows f perforate section of the mandrel tubezo .yvlreh'is 5dr. -pa'stthe cinch bands SUFSO from sectionto section.y of rounded by the sheath 21 so that, l.the latterrgay v,be "30 -the Asheath 21 via the flow ducts along the sides ofthe inched up or fied aany desired or sleetedpoimlbywany Ilands .provided by the longitudinally-extending rod-s .of the cinch bands 5e preferably, the .land rods 52.52 #S2-#52 and thus the shell is-securely tied to the mandrel.

are provided as elements of arelatvively heavy hierheen. Repeated'blows on the hamer base 45 which react struction Vor standard screen wrappedehoptrherexgerior against thel anvil y42 drive the mandrel tube 20 into the surface of the mandrel tube 20 andifhaYillgits transverse "35' fgl'oundrwiththebot P31157 leading it and With the Pile elements 53-53 also of about 0 125" redjsjk,exreud :shell49 carried intothe soil-with maintenance of pressure iing circumferentially about the mandrel tube. `Such-.mesh kinctltvcen the shell .and the lsoil. Assume in this `manner construction may be readily applied the exteriorI 91 tthat'thepile'shell 49 and the boot pan 57 vare driven lby :face of the steel mandrel tube 2.0 inatrelatiyejty, frite the mandrel assembly tothe position depicted ih Fis 2. .mannen such as byWl-appng a rectangulaI-sect-ign-lof it iS DOW deSI'ed'tO'pIOVide the With a. fotil'lg screen thereaboutand spot-welding it atvarious points-to 'of'base of Concreto ofA good load-bearing CharaCfSiCS, the exterior surface of themandrel tube. *The ;cirenmvthe lhammer:hase fwi11 then'heraised t0 Carry with it ferentia-lly-cxtending rod elements 5353 not only-.serve the 'anvil 42 to all elevated Position, Such 3S 'that dem rie the 1ongitudina1iy-extendingrod elements :52,952 `45 pictfd `tu Fie- 3- During this time the ttexible ties or 'together to simpfy their mounting, upon-the. exterior. sur, f Ichains 47,. 47 becometaut to raisel the core tubel 22 to 4an lface of the mandrel tube 20 but also astpmjeeringel felevated position so that its bottom tamping end 34 is .ments .which Win more securely anchor the ,wan 05111@ VV'raised a distance of, for example, about 3 abovevthe boot sheath 21 to the mahdre1 mbe at aeineh' band tir-..asfrhe P81151 t1 he'apparatus iS then re'adied for Supply 0f unset cinch band, when tightened up, wi11'foreetr-he eireumfer- 50 footingconcrete and the tamping thereof into a pile base. Vential rods into the elastic f sheath wall. Sincerthetciri dit Will be understood from Fig 3 that the raised anvil cumfercntal rods 53-53 are located outward of the 'L42 is Positioned an appreciable distance above d1@ toP flongitudinallyextending rods 5;. 52 asshown, jtheydo end .'32 .of the core tube so that the latter is open `and not'interfere with the maintenance of ilow fductsfatl'east accessibi- A`=Chafge oflnseffoiadvoiy dry Concreto may along the sides of the longitudinally-extending rods. It t55 the fSuP-Plid to the Open tOP end of the Core. tube by will be understood from Fig. 4 that Witha relativelyfithic i i Til-dy ditblo means, Suoh as a dump bucket .53, Which sheath wan of umited elasticity, tightening of theieinch mayb@ carried :by any Suitable Crane *Cable harness, YSuch band about the sheath 21 possibly wllnot-'cause'the *'35 that indicated at 59- The dump biloket 53 may tbe jsheathwall to be distorted toa degree of dre'ctlcontad providedwith suitable trip mechanism, such as a pair of v with the exterior surface of 'the mandrelitubegxzl) at any `6l) 'laterally-@dood arms 60 tied together by a transverse rod point but merely te bulge toward it, .agdepdqdl qnfahy l ,61, whlchmay be caught under the edge of the `sectorof event, should the sheath wall be 'of `suc'e:h"limited thickness 'the lateral ange -33 on the IOP end of the core tube 22 '01'. or of such elasticity as vto cause thecinc'h yband-*50 .to disany'pmjfetion Provided there@ for that Purpose' AS a' 'tort its interior surface to `contact of the exterior, surface 'msi-llt; the'dump ybilloko Win11 tbe tiPPed 3S indicated in ,of the mandrel tube 20 at a snugging or'tyin'g'lo-cal'ity 65 im in Eg 3 to denver .lts contents down the fore tube A22. When the core tube 22 was lifted by the ties .47,l 47, force of gravity caused the valve head`38to drop .out of the valve passage 36 and open it with kthe Vvalve Y, stem'head 40 serving as a limiting stop. The dumped charge of concrete will fall down the core tube 22 and .45 again `to rest nponthe .Core tubetop .end 3,2 and lcach beguided'by the funnel section 37 to and through'the .outlet passage provided by valve seat 36 to collect at 62 .ontheboot pan, as depicted in Fig. 3.

vThe anvil -42 will then be lowered with the hammerbase :ananas and tamping it may be repeated to accumulate a base ofV desired size and shape. The boot pan will be lost in the so formed base mass andin no way interferes with. the load-bearing elliciency of the tamped base. Its losslentails' no appreciable economic loss since such boot pans are of low cost. Y f

It will be understood that the flow duct-forming and maintaining, longitudinally-extending lands of the exterior surface of the mandrel tube maybe in a variety of forms.V

For example, as proposed in' Fig.v 5, a relatively heavy mandrel tube 120 may be provided withaseries ofcircumferentially-spaced, longitudinally-extending grooves 63-63 to provide therebetween longitudinally-extending,

' circumferentially-spaced raised ribs or lands'` 152-452 which will serve to provide and maintain flow ducts in the bottoms of the grooves at a snugging or pinchinglocality for intercommunicating adjacent sections of the sheath 21.

If it is desired to lform a bulbous base Vof footing concrete for the pile, which may be advisable in soft `or lo'ose soil or water-bearingtsand, the procedure of delivering a charge of footing concrete down the core tubef22 and tamping it with the tamping bottom end` 34 of the latter will be repeated to form an accumulated bulbous inass 64 of concrete, as depicted in Fig. 6. Then, the pile: shell 49 `may have its bottom end 65 driven into the bulbous mass `crete is tampeclv out by the tube 22,7the'bottom end of the liner or slip tube, as it i E'As indicatediin Fig. ll, when such a liner or slip tube a charge162 of unset footing contamping end 34 of the core 66v is employed `and slidesV out of th .bottom end of the mandrel tube, desirablyA begins spreading to permit the desired spread of the tamped concrete and eventually with tamping of successive charges `of footing concrete, such liner or slip tube, in distorte'dcondition, is lost in the base mass without having interfered with proper shaping and formation of the` latter. If desired, slippage between the mandrel tube- 20 and the liner or slip tubeV 66 may be assured or increased by a few dabs of grease to the exterior surface of Vthelatter before its insertion into the bottom end of the former.

It is to be'understood that the tamping means provided on the bottom end of the core tube is not limited to the form proposed in Figs. 1, 3,6, 7 and ll. For example, as indicated in Fig. 12, core tube 122 may be provided by athickened wall section 134, the exterior surface of which is substantially cylindrical and `,coextensive with the cylindrical outer surface of the main portion of the core tube but with its internal diameter progressively decreased so asto provide a funnel-shaped outlet passage 137; As a result, such tamping means provides on the bottom end of the core tube a tamping face in the form of a circular zone 71 of appreciable width which will 64 `by further hammer blows upon the mandrel Vtube top Y end 23`th'rough the core tube flange 33 and 'the anvil 42, such as to the position indicated inFig. 6. ':1 1

After the pile base or footing has been formed and the pile shell 49 set to the satisfaction ofthe engineer, the successive sections of the sheath 2-1 are vdeflated,ssuch as by turning the valve 31 to the bleed or reliefsposition. This frees the mandrel tube 20 "from theshell` 49.; @The core tube 22,` the mandrel `tube l20, and the .confining section 54 are then pulled.` Thereafter, concretexwill be cast into the pile shell r49 to form the cast-in-place-concretepile. l .1, f..

If it is desired to avoid any tendency for footing concrete, `while ibeing `tamped, todrag the mandrel tube 20 and the shell 49 downwardwith it byfrictionalcontact with the inner wall of the bottom end 25 of the mandrel t tube, this may be avoided by providing liner means preferably in the` form lof a relatively short tubular `section 66 inserted between thel inner surface of themandreltube and the outer sm'face of the coretube. The'liner means 66 thus may be in the form of a slip tube and may be formed of relatively thin black iron or deadsteeL Slip tube 66 may be constructed from a blank,`s iuc.has :that

indicated in Fig. 8, consisting of an elongated rectangular sheet 67 having extending from one side edge thereof longitudinally-spaced tabs 68,-68. rlhe blank shown in Fig. 8 may then be curved into a tubular section, such as that depicted in Fig. 9, and there is no need tosecure together the juxtaposed `end edges 69 and 70`l Infact,

v it is desired to leave the Vend edges free of each other so `that such liner means or slip tube may be. distorted and spread in the tamped formation of the base toavoid .interference with` the tamping and forming procedure 4and it, `like the boot 4pan 57, will be lost in the base mass. j The liner means or slip tube 66 may Vbe` provided, in the form shown in Figf9, and delivered to the jobwhere theV tabsA 684-63 may easily bent laterally outward, such as byfhammer blows, to form radiating arms which will seat in the flanged boot pan 57 to assure Vapprintimately coaxial arnmgementrtherein and proper concentric posihoning with respect to the mandrel tube 20 and the core tube 22. When such liner means or slip `tube is employed, the core tube may be of smaller O. D.to provide" the bottom of the core tube. V

effectively tamp the footing concrete when successive blows are appliedto the core tube 122. Such tamping means as proposed in Fig. 12 may, if desired, be provided by a separate casting fastened to or mounted upon It is sometimes desired to use a pre-cast base in the form of a point, such as that Vproposed in Fig. l2, and it will be understood that the pile-driving apparatus of the present invention, in any of the forms proposed above, iS adapted to the use of such a point. As there suggested, a pre-cast point 72 may be in the form of a cast body of concrete having a leading pointed end 73 and a back end inthe form of a cylindrical projection 74 which is loosely receivableinto the bottom end 25 of the mandrel such point will be projection 74 .scope of the invention,

tube, so as to be driven ahead of the latter. Of course,

of a diameter sufficiently large to assure` that the point body below the cylindrical back end will extend radially beyond the bottom edge of the pile `shell 49 to serve the same purpose as the boot pan 57 during the driving of the shell.

It,will thus be seen that vthe objects set forth above, among those made apparent from the preceding description, are eiciently attained and, since certain changes the constructions set forth without departing from the it is intended that all matter contained in the above Adescription' or .shown in the accomi panying drawings shall be interpreted as illustrative and not in a limiting sense.

`tures ofthe invention herein Itis also to be understood that the following' claims areintendedto cover all of thegcneric and specific feadescribed, and all statements ofthe scope of the invention which, as a matter 0f language, mightk be saidto vfall therebetween.

.Having described my invention, what IclaimV as new and desire to secure by Letters Patent is: 65

, an elongated,. rigid, drivable,

, anintervening imperforate sidewall section of appreciable length; an elongated,

interiorly-unobstructed core tube ,Offan outer diameter appreciably less than the inner `diameter votsaid mandrel tube loosely telescoped into Isaid mandrel tube and having an open upper end to receive and deliver to .its bottom end charges of unset footing` concrete; abutment means on the upper ends of said core; and mandrel tubes to limit telescope of the former downj` l into the latter while permitting ready upwardwithdrawal of said core tube; tamping means provided on the bottom end of said core tube and having a ow passage extending therethrough to deliver charges of unset footing concrete therebelow; anvil means removably supported by the upper end of said mandrel tube which when lifted to a feed position uncovers the open upper end of said core tube to permit dumping thereinto of charges of unset footing concrete; an elongated, imperforate, inflatable tubular sheath of elastic material covering the imperforate section of said mandrel tube and anchored at its top and bottom ends in a fluid-tight manner to said imperforate mandrel tube section to define therebetween an air chamber, said sheath being expandable upon inflation of said chamber into intimate supporting contact with the inner wall of surrounding pile shell means; air supply and exhaust conduit means exterior of said mandrel tube connected below said anvil means to the upper end of said chamber Without interfering with telescope of said core tube into said mandrel tube; at least one cinch band snugged about said inflatable sheath to there clamp the latter to the exterior surface of said mandrel tube section for distributing longitudinal drag by surrounding shell means during driving; and longitudinally-extending lands located on the the exterior of said mandrel tube beneath said sheath extending axially beyond the top and bottom edges of said cinch band providing past the latter along the sides of said lands fluid ways to assure inflation and deation of all sections of said sheath.

2. A pile driving apparatus comprising, in combination; an elongated, rigid, drivable, unblocked mandrel tube having an open upper driving end, an open lower end and an intervening imperforate sidewall section of appreciable length; an elongated, interiorly-unobstructed core tube of an outer diameter appreciably less than the inner diameter of said mandrel tube loosely telescoped into said mandrel tube and having an open upper end to receive and deliver to its bottom end charges of unset footing concrete; abutment means on the upper ends of said core and mandrel tubes to limit telescope of the former down into the latter while permitting ready upward withdrawal of said core tube; tamping means provided on the bottom end of said core tube and having a flow passage extending therethrough to deliver charges of unset footing concrete therebelow; anvil means removably supported by the upper end of said mandrel tube which when lifted to a feed position uncovers the open upper end of said core tube to permit dumping thereinto of charges of unset footing concrete; an elongated, imperforate, inflatable tubular sheath of elastic material covering the imperforate section of said mandrel tube and anchored at its top and bottom ends in a fluid-tight manner to said imperforate mandrel tube section to dene therebetween an air chamber, said sheath being expandable upon inflation of said chamber into intimate supporting contact with the inner wall of surrounding pile shell means; air supply and exhaust conduit means exterior of said mandrel tube connected below said anvil means to the upper end of said chamber without interfering with telescope of said core tube into said mandrel tube; at least one cinch band snugged about said inflatable sheath to there clamp the latter to the exterior surface of said mandrel tube section for distributing longitudinal drag by surrounding shell means during driving; and a plurality of circumferentially-spaced, longitudinally-extending rods located on the exterior surface of and extending through a major portion of the length of said imperforate mandrel section to lie beneath said cinch band and the intervening sheath with maintenance of fluid ways along the sides of said rods past said cinch band.

3. A pile driving apparatus comprising, in combination; an elongated, rigid, drivable, unblocked mandrel tube having an open upper driving end, an open lower end and an intervening imperforate sidewall section of appreciable length; an elongated, interiorly-unobstructed core tube of an outer diameter appreciably less than the inner diameter of said mandrel tube loosely telescoped into said mandrel tube and having an open upper end to receive and deliver to its bottom end charges of unset footing concrete; abutment means on the upper ends of said core and mandrel tubes to limit telescope of the former down into the latter while permitting ready upward withdrawal of said core tube; tamping means provided on the bottom end of said core tube and having a ow passage extending therethrough to deliver charges of unset footing concrete therebelow; anvil means removably supported by the upper end of said mandrel tube which when lifted to a feed position uncovers the open upper end of said core tube to permit dumping thereinto of charges of unset footing concrete; an elongated, imperforate, inflatable tubular sheath of elastic material covering the imperforate section of said mandrel tube and anchored at its top and bottom ends in a fluid-tight manner to said imperforate mandrel tube section to define therebetween an air chamber, said sheath being expandable upon inflation of said chamber into intimate supporting contact with the inner wall of surrounding pile shell means; air supply and exhaust conduit means exterior of said mandrel tube connected below said anvil means to the upper end of said chamber without interferring with telescope of said core tube into said mandrel tube; at least one cinch band snugged about said inflatable sheath to there clamp the latter to the exterior surface of said mandrel tube section for distributing longitudinal drag by surrounding shell means `during driving; and a wrap of relatively heavy mesh means on the exterior surface of and extending over the major portion of said imperforate mandrel section and beneath said elastic sheath, said mesh means having circumferentially-spaced, longitudinally-extendng rod elements adjacent said mandrel section surface and mandrel-encircling, axially-spaced rod elements on the outside of said longitudinally-extending rod elements with the latter providing longitudinal fluid Ways beneath said sheath and cinch band and said mandrelencircling rod elements providing sheath-anchoring projecting means which embeded into said sheath upon tightening of said cinch band.

References Cited in the le of this patent UNITED STATES PATENTS 977,356 Withrow Nov. 29, 1910 2,334,386 Cortella Nov. 16, 1943 2,741,093 Riker Apr. 10, 1956 FOREIGN PATENTS 761,693 Germany Jan. 19, 1953 1,047,824 France July 29, 1953 

